1. Field of the Invention
The present invention relates to electrical/electronic test equipment, and more particularly to operational test equipment for electrical/electronic test equipment.
2. Description of the Related Art
During or after the manufacture of many electrical and electronic products a series of safety tests are performed to ensure proper operation of the products under specific conditions. These test conditions are described in many industry standards, including IEC 60-950, 61010-1, 60335-1, 60601, EN50116, EN50106, and EN50114-1, the disclosures of which are hereby incorporated by reference in their entirety. Two safety tests that are performed on electronic products are a dielectric withstand (“hipot”) test and a ground continuity test. These tests are referred to in the European Standard documents listed above as the Electric Strength test and the Earth or Earthing Continuity test.
The electric strength test recited in EN50116 includes applying to the electronic equipment under test a sinusoidal AC voltage at 50 or 60 Hz of at least 1500 Volts for a product having basic insulation where the passing requirements are that no insulation breakdown shall occur during the test. EN50116 defines an insulation breakdown as any significant increase from the steady state current measured during the electric strength test. The EN50106 and EN50144-1 documents both list a test voltage of 1000 Volts for a product having basic insulation with a similar breakdown requirement.
The earth continuity test of EN50144-1 comprises passing a current of at least 10 Amps between the earthing/grounding terminal or earthing/grounding contact of the electronic product under test and accessible metal parts which need to be grounded for safety reasons. The voltage drop between the ground terminal or contact and the accessible metal part is measured, and the resistance is calculated from this voltage drop and the level of current supply. EN50144-1 sets this resistance at a maximum of 0.3Ω while EN50106 cites a limit of 0.2Ω for appliances having a supply chord, and EN50116 lists a limit of 0.1Ω. An additional safety test typically performed on electronic products is that of exceptional levels of leakage current from the primary circuits to the ground terminal, 1.5 mA for example, in the product under test.
Several vendors supply testers that perform one or more of these tests, and their operation is well known in the art. Due to their importance in the verification that manufactured products are safe for consumer use, it is critical that the testers function properly and do not indicate a passing result when the product under test is actually in a failing condition.
It will be appreciated that a device for verifying the integrity of an electronics tester would be valuable to both the manufacturers and users of the electronics testers.